Device for detecting blown fuses



Nov. 17, 1953 A. LANG 2, ,789

DEVICE FOR DETECTING BLOWN FUSES Filed May 18. 1951 INVENTOR. ADOLPH LANG AGENT Patented 'Nov. 17, 1953 UNITED STATES PATENT OFFICE DEVICE FOR DETECTING BLOWN FUSES Adolph Lang, New York, N. Y.

Application May 18, 1951, Serial No. 226,997 1 Claim. (Cl. 200-121) My present invention relates to a method of and a device for facilitating the discovery of a blown electric safety fuse among a number of such fuses arrayedon a panel, in a fuse box or on some other support.

In private residences, in apartment houses and particularly in factories and other commercial establishments the blowing of a fuse due to accidental overloading of a power line is often a source of considerable annoyance, as well as costly delay, on account of the time required in identifying the destroyed fuse among a group of intact ones located close by, in view of the fact that a large number of such fuses are usually placed next to one another in poorly illuminated locations such as basements, Stairways and the like.

The general object of my invention is to provide a method of and means for avoiding the above inconveniences by greatly facilitating visual inspection of fuses and enabling the virtually instantaneous determination of the intact or blown condition of a fuse even at considerable distance and under poor lighting conditions.

In accordance with the invention I provide an attachment having a phosphorescent surface adapted to be so positioned on the fuse as to be conveniently visible from without (at least in the excited state) while being exposed to light rays from the spark caused by the melting of the fusible metal strip by excessive line current. I have found that the glow of the phosphorescent surface, when thus excited, will remain visible for a sufficient length of time (up to several hours) to indicate to an observer the fact that a flash has occurred in the fuse.

The invention will be described with reference to the accompanying drawing in which:

Fig. 1 is a longitudinal section through a conventional electric fuse, provided with a phos phorescent attachment representing an embodiment of the invention;

Fig. 2 is a side elevation of the attachment shown in Fig 1;

Fig. 3 is a rear view of the fuse with attachment shown in Fig. 1;

Fig. 4 is a front view of the attachment;

Fig. 5 is a longitudinal section through a fuse similar to that of Figs. 1 and 2 (but taken at right angles to the section of Fig. l). the fuse being provided with a modified phosphorescent attachment according to the invention;

Fig. 6 is a front view of the fuse with attachment shown in Fig. 5; and

2 F1Fig. 7 is a section taken on the line of Referring first to Figs. 1-4, there is shown a conventional safety fuse l0 comprising a body II of insulating material, a glass housing l2 receiving part of said body, a metal shell l3 threadedly engaging the housing l2 and bearing against a shoulder 14 of the body II to keep same in engagement with the housing l2, and a fusible strip I5 having one end conductively secured to central terminal I6 and having its other end in contact with the shell l3.

Mounted on the front face of the housing I2 is an atachment comprising a ring 2| slitted at 22a, 22b and 220 to provide two resilient wings 23a, 23b adapted to engage the flange ll of the housing; it will be noted that with this arrangement a tight fit may be obtained even in the event of substantial variations of fuse size, this being an important advantage on account of the fact that fuses even of common manufacture are found to vary considerably in circumference. Lodged in the ring 2| are two parallel, transparent disks 24, 25 (e. g. of resinous material) separated by a spacing ring 26. Inner disk 25 carries a phosphorescent coating 21 facing the outer, protective disk 24.

When the fuse I0 is overloaded, the strip I5 will melt with a flash causing intense light to penetrate the glass housing I! and the disk 25, thereby exciting the phosphorescent layer 21 to prolonged luminescence. From the glow of the surface 21 an observer will then be able to determine the fact that the fuse has been put out of commission. Ring 2 l, which is of opaque material, acts as a light shield to prevent similar attachments on adjacent fuses from becoming excited upon blowing of the fuse I0.

In Figs. 5-7 the attachment 20 has been replaced by an attachment in the form of an annular insert 3| bearing on its inner surface a phosphorescent coating 31. The insert 3| fits snugly inside the chamber I8 of the fuse housing I! (see Fig. 1) and is thermally shielded from the fusible strip l5 by a transparent disk 34. Disk 34 is preferably cut away at 32a, 32b (Fig. 7) and provided with stepped portions 33a, 33b to establish communication between the chamber 18 and the space l8 adjacent the strip l5.

The operation of the device shown in Figs. 5-7 is in principle identical with that of the one described in connection with Figs. 1-4,- with the additional advantage that the strip l5 remains visible as clearly seen in Fig. 6. The condition of the fuse may thus be readily ascertained in the normal manner after the luminescence of the layer 31 has vanished. A similar advantage may, or course, be had with the attachment of Fig. 1 by omitting a central portion oi. the layer 21.

The annular insert 3|, being opaque, again acts as a light shield to prevent excitation of ad- Jacent Iuse attachments.

' Although the invention has been described with reference to only two specific embodiments. it is to be understood that the same may be modified in various ways without thereby departing from the scope of the appended claim. For example, some or all of the light-transmissive members of the attachments described, such as disks 24, 25 and 34, may be made translucent instead of transparent, if desired.

I claim:

As a new article of manufacture, an attachment for indicating the blowing of an electric fuse of the type having a closed housing provided 4 with a window surrounded by a transparent or translucent annular flange, said attachment comprising a ring of opaque material slitted perimetrally and in axial direction, thereby forming a pair of outwardly movable wings each extending over a major fraction of a quadrant of said ring and adapted resiliently to engage said flange, a disk of light-transmissive material surrounded by and supported on said ring, and a phosphorescent coating on said disk, said ring shielding said coating from excitation by a hash from an adjacent fuse.

ADOLPH LANG.

References Cited in the file of this patent UNITED STATES PA'I'ENTS Number Name Date 1,386,241 Deck Aug. 2, 1921 1,666,339 Miller Apr. 17, 1928 

